Integrally blow-moulded bag-in-container having interface vents opening to the atmosphere at location adjacent to bag&#39;s mouth, preform for making it; and processes for producing the preform and bag-in-container

ABSTRACT

The invention is an integrally blow-moulded bag-in-container and preform for making it. The bag-in-container has an inner layer forming the bag and an outer layer forming the container, and a mouth fluidly connecting the volume defined by the bag to the atmosphere. The container further has at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere, wherein the at least one vent runs parallel to the interface between inner and outer layers and opens to the atmosphere at a location adjacent to, and oriented coaxially with the bag-in-container&#39;s mouth. Processes for manufacturing a preform and a bag-in-container as defined above are defined too.

This application is a divisional application of U.S. Ser. No.12/450,896, filed on May 24, 2010, which was a 35 U.S.C. §371 nationalphase conversion of PCT/EP2008/054765, filed on Apr. 18, 2008, whichclaims priority to U.S. application Ser. No. 11/785,747, filed on Apr.19, 2007.

FIELD OF THE INVENTION

The present invention relates in general to new developments indispensing bag-in-containers and, in particular, to the interface ventsdesign which allows control of the pressure at the interface between aninner layer (the bag) and an outer layer (the container) of saidbag-in-container, in order to separate the inner layer from the outerlayer and collapse the inner bag. It also relates to a method forproducing said bag-in-containers and, in particular, to preforms usedfor their production, as well as a method for producing said preform.

BACKGROUND OF THE INVENTION

Bag-in-containers, also referred to as bag-in-bottles or bag-in-boxesdepending on the geometry of the outer vessel, all terms consideredherein as being comprised within the meaning of the termbag-in-container, are a family of liquid dispensing packaging consistingof an outer container comprising an opening to the atmosphere—themouth—and which contains a collapsible inner bag joined to saidcontainer and opening to the atmosphere at the region of said mouth. Thesystem must comprise at least one vent fluidly connecting the atmosphereto the region between the inner bag and the outer container in order tocontrol the pressure in said region to squeeze the inner bag and thusdispense the liquid contained therein.

Traditionally, bag-in-containers were—and still are—produced byindependently producing an inner bag provided with a specific neckclosure assembly and a structural container (usually in the form of abottle). The bag is inserted into the fully formed bottle opening andfixed thereto by means of the neck closure assembly, which comprises oneopening to the interior of the bag and vents fluidly connecting thespace between bag and bottle to the atmosphere; examples of suchconstructions can be found inter alia in U.S. Pat. No. 3,484,011, U.S.Pat. No. 3,450,254, U.S. Pat. No. 4,330,066, and U.S. Pat. No.4,892,230. These types of bag-in-containers have the advantage of beingreusable, but they are very expensive and labour-intensive to produce.

More recent developments focused on the production of “integrallyblow-moulded bag-in-containers” thus avoiding the labour-intensive stepof assembling the bag into the container, by blow-moulding a polymericmultilayer preform into a container comprising an inner layer and anouter layer, such that the adhesion between the inner and the outerlayers of the thus produced container is sufficiently weak to readilydelaminate upon introduction of a gas at the interface. The “innerlayer” and “outer layer” may each consist of a single layer or aplurality of layers, but can in any case readily be identified, at leastupon delamination. Said technology involves many challenges and manyalternative solutions were proposed.

The multilayer preform may be extruded or injection moulded (cf. U.S.Pat. No. 6,238,201, JPA10128833, JPA11010719, JPA9208688, U.S. Pat. No.6,649,121). When the former method is advantageous in terms ofproductivity, the latter is preferable when wall thickness accuracy isrequired, typically in containers for dispensing beverage.

Preforms for the production of integrally blow-moulded bag-in-containersclearly differ from preforms for the production of blow-mouldedco-layered containers, wherein the various layers of the container arenot meant to delaminate, in the thickness of the layers. Abag-in-container is comprised of an outer structural envelope containinga flexible, collapsible bag. It follows that the outer layer of thecontainer is substantially thicker than the inner bag. This samerelationship can of course be found in the preform as well, which arecharacterized by an inner layer being substantially thinner than theouter layer. Moreover, in some cases, the preform already comprisedvents which are never present in preforms for the production ofco-layered containers (cf. EPA1356915).

One redundant problem with integrally blow-moulded bag-in-containers isthe formation of the interface vents. Several solutions were proposedwherein the vent was formed after the bag-in-container was blow-moulded,as in U.S. Pat. No. 5,301,838, U.S. Pat. No. 5,407,629, JPA5213373,JPA8001761. This approach has of course the disadvantages that itinvolves an additional production step, and the danger of piercing thebag. Indeed these solutions have in common the formation of a holenormal to the outer containers wall and great accuracy is required notto degrade the inner layer's wall.

In EPA1356915 and U.S. Pat. No. 6,649,121, the preform is formed byinjection moulding the outer layer first, followed by injection mouldingthe inner layer over the outer layer. During injection moulding of thelayers, ventilation holes normal to the outer layer's wall are formedwith protruding pins, which are flush with the inner surface of the thusobtained outer layer. The over-injected inner layer is not affected bythe pins and this method solves the problem associated with the risk ofdamaging the inner bag during vents formation. The ventilation holesmust be positioned close to the region of the container's mouth in anarea of no or little stretching during the blow-moulding operation.

The venting holes described in EPA1356915 and U.S. Pat. No. 6,649,121,however, are not suitable for being connected to a source of pressurizedgas to three delamination and squeezing of the inner bag. Furthermore,the inner and outer layers are little or not stretched in the regionclose to the container's mouth resulting in thicker and more rigid wallsin this region than in the container's body. Consequently, a higherpressure would be required to delaminate the inner from the outer layersby blowing compressed air through the vents in a direction normal to theinterface, as required in beg-in-containers for dispensing beverage likebeer and sodas.

JPA10180853 discloses an integrally blow-moulded bag-in-container,wherein the preform consists of an assembly of an inner preform fittedinto an outer preform such as to have a cavity transverse to the outercontainer's wall at a location very close to the preform assembly'smouth. Upon blow-moulding, said vent is maintained in the thus producedbag-in-container. It should be noted that the thickness of the preform'swalls disclosed in JPA10180853 varies locally which can lead to seriousprocessing and reproducibility problems of the final bag-in-containerupon blow-moulding.

In order to optimize delamination of the inner and outer layers uponblowing pressurized gas into the vents, said vents should preferably ranparallel to the interface between the two layers to provide a wedgeeffect. In the solutions proposed in the prior art relating tointegrally blow-moulded bag-in-containers However, the vents runperpendicular to the interface and open to the atmosphere through a holeacross, and normal to the outer container's wall, therefore providing nowedge effect and thus reducing the efficacy and reproducibility of thedelamination of the inner bag from the outer container.

Bag-in-containers for beverage, like beer or sodas are usuallypositioned in a specially designed appliance comprising a dispensingpassage to be connected to the mouth opening of the inner bag and asource of pressurized gas (generally air) to be connected to the ventsopening(s). For reasons of compactness of the appliance, the ventsdesign is restricted and should preferably open to the atmosphere at alocation adjacent to the bag-in-container's mouth and oriented along thesame axis as the latter, so as to allow all the piping to be bundledtogether. Such design follows the traditional beer keg interface in thisregard, which is of course an advantage as it allows the replacement ofa traditional keg by an integrally blow-moulded bag-in-container,without having to change the dispensing appliance.

It follows from the foregoing that there remains a need in the art foran integrally blow-moulded bag-in-container dispense package that allowsoptimization of the delamination of the inner bag from the outercontainer upon injection of a pressurized gas at the interface thereofand, at the same time, which can be used with the existing dispensingappliances.

SUMMARY OF THE INVENTION

The present invention is defined in the appended independent claims.Preferred embodiments are defined in the dependent claims. In particularthe present invention relates to an integrally blow-mouldedbag-in-container having an inner layer forming the bag and an outerlayer forming the container, and a mouth fluidly connecting the volumedefined by the bag to the atmosphere. The container further includes atleast one interface vent fluidly connecting the interface between innerand outer layers to the atmosphere, wherein the at least one vent runsparallel to the interface between inner and outer layers and opens tothe atmosphere at a location adjacent to, and oriented approximatelycoaxially with the bag-in-container's mouth.

The present invention also concerns a preform for blow-moulding thebag-in-container of the present invention. The preform includes an innerlayer and an outer layer, and a body, a neck region, and a mouth fluidlyconnecting the space defined by the inner layer to the atmosphere,wherein the inner and outer layers are connected to one another by aninterface at least at the level of the neck region. The preform includesat least one interface vent running parallel to the interface andopening to the atmosphere at a location adjacent to, and orientedcoaxially with the preforms mouth.

The inner and outer layers of the preform (and consequently of thebag-in-container) of the present invention may consist of different orthe same materials. The two layers of the preform may be connected by aninterface throughout substantially the whole inner surface of the outerlayer. Inversely, they may be separated over a substantial area of thepreform's body by a gap containing air and which is in fluidcommunication with at least one interface vent. The preform may be anassembly of two separate inner and outer preforms or, alternatively,they may be an integral preform obtained by injection moulding one layeron top of the other.

The vent preferably is in the shape of a wedge with the broad side atthe level of the opening thereof and getting thinner as it penetratesdeeper into the vessel, until the two layers meet to form an interface.The container may comprise one or several vents evenly distributedaround the lip of the bag-in-container's mouth.

One advantageous method to produce the bag-in-container of the presentinvention comprises the following steps:

-   -   providing a preform as described above, wherein a gap containing        air separates the inner and outer layers over a substantial area        of the preforms body and wherein said gap is in fluid        communication with at least one interface vent;    -   bringing said preform to blow-moulding temperature;    -   fixing the thus heated preform at the level of the neck region        with fixing means in the blow-moulding tool;    -   blow-moulding the thus heated preform to form a        bag-in-container;        wherein,    -   in a first stage, a gas is blown into the space defined by the        inner layer to stretch the preform, whilst the air in the gap        separating the preform inner and outer layers is prevented from        being evacuated by closing said at least one preform interface        vent with a valve located in said fixing means; and    -   in a second stage, when the air pressure building up in said gap        reaches a preset value, the valve opens thus allowing evacuation        of the air enclosed in the gap.

A particularly preferred embodiment of the preform according to thepresent invention is an integral two layer preform which may bemanufactured by a process comprising the following sequential steps:

-   -   injection moulding the preform's inner layer onto a core;    -   injection moulding the preform's outer layer onto the inner        layer;    -   extracting the thus formed preform from the core,        wherein said core is provided at the base thereof with at least        one pin suitable for forming an interface vent running parallel        to the interface between said first and second layers and        opening to the atmosphere at a location adjacent to, and        oriented coaxially with the preform's month.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional representation of a firstembodiment of a preform according to the present invention and thebag-in-container obtained after blow-moulding thereof.

FIG. 1B is a schematic cross-sectional representation of a secondembodiment of a preform according to the present invention and thebag-in-container obtained after blow-moulding thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to appended FIGS. 1A and 1B, there is illustrated anintegrally blow-moulded bag-in-container (2) and a preform (1)&(1′) forits manufacturing. The preform (1) comprises an inner layer (11) and anouter layer (12) joined at least at the level of the neck region (6) byan interface (shown on the right hand side). The region between innerand outer layers (11) and (12) may either consist of an interface (14)wherein the two layers are substantially contacting each other, orcomprise a gap (14) in fluid communication with at least one vent (3).Said vent (3) comprises an opening (4) located adjacent to, and orientedcoaxially with said preforms mouth (5).

The preform may consists of an assembly of two independent preforms (11)and (12) produced independently from one another and thereafterassembled such that the inner preform (11) fits into the outer preform(12). This solution allows for greater freedom in the design of the neckand vents, as well as in the choice of materials constituting eachpreform component. Alternatively, it can be an integral preform obtainedby injection moulding one layer on top of the other. The latterembodiment is advantageous over the assembled preform in that itcomprises no assembly step and one production station only is requiredfor the preform fabrication. On the other hand, the design of the ventsin particular is restricted and the respective melting temperatures ofthe inner and outer layers must be carefully matched depending on whichlayer is injected first; the rule of thumb being that the layer beinginjected first generally requires a higher melting temperature.

The inner and outer layers of the preform (1) may consist of differentmaterials or the same material. In case different materials are used,some requirements must be fulfilled depending on the process parametersin the injection moulding of the preform as well as in the blow-mouldingof the bag-in-container. It is important of course that both materialsmay be processed in a rather similar process window and that they willnot form too strong an interface which would not satisfactorily releaseupon injecting pressurized gas at the interface.

Alternatively and surprisingly, good results can be obtained also withpreforms wherein both inner and outer layers consist of the samematerial. The same polymer is considered in contact on either side ofthe interface between the inner and outer layers in the following cases:

-   -   inner and outer layers consist of the same material (e.g.,        PET_(inner)−PET_(outer), regardless of the specific grade of        each PET); or    -   the inner and outer layers consist of a blend or copolymer        having at least one polymer in common, provided said polymer in        common is at the interface, whilst the differing polymer is        substantially absent of the interface (e.g., 0.85 PET+0.15        PA6)_(inner)(0.8 PET+0.2 PE)_(outer).        The presence in a layer of low amounts of additives is not        regarded as rendering the material different, so far as they do        not alter the interface substantially.

Preferred materials for the preform and bag-in-container of the presentinvention are polyesters like PET, PEN, PTT, PTN; polyamides like PA6,PA66, PA11, PA12; polyolefins like PE, PP; EVOH; biodegradable polymerslike polyglycol acetate (PGAc), polylactic acid (PLA); and copolymersand blends thereof. In case different materials are used for the innerand outer layers, their optimal blow moulding temperatures should notdiffer from one another by more than about 70° C. preferably 40° C.,most preferably 10° C., and ideally should have the same blow-mouldingtemperature. The layer's temperatures may be determined byIR-measurement.

The two layers (11) and (12) of the preform may be connected by aninterface (14) throughout substantially the whole inner surface of theouter layer (cf. (1) in FIG. 1A). Inversely, they may be separated overa substantial area of the preforms body by a gap (14′) containing airand which is in fluid communication with at least one interface vent (3)(cf. (1′) in FIG. 1B). The latter embodiment is easier to realize whenusing a preform assembly designed such that the inner preform is firmlyfixed to the outer preform at the neck region (6) and a substantial gap(14) may thus be formed between inner and outer layers (11) and (12).

A release agent may be applied at the interface on either or bothsurfaces of the inner and outer layer, which are to form the interfaceof the bag-in-container, in the ease the outer layer is injectionmoulded onto the inner layer, the release agent can be applied at theouter surface of the inner layer prior to moulding the outer layer. Anyrelease agents available on the market and best adapted to the materialused for the preform and resisting the blowing temperatures, likesilicon- or PTFE-based release agents (e.g., Freekote) may be used. Therelease agent may be applied just prior to loading the preforms into theblowmoulding unit, or the preforms may be supplied pretreated.

The application of a release agent is particularly beneficial withrespect to the design of the inner layer. Indeed, lowering theinterferential adhesive strength facilitates delamination of the innerlayer from the outer layer and hence reduces stress exerted on the innerlayer upon delamination, as such the inner layer can be designed verythin and flexible without risking that the inner layer is damaged upondelamination. Clearly, the flexibility of the inner bag is a keyparameter for the liquid dispensing and moreover costs savings can beachieved in terms on material savings when the inner layer can bedesigned very thin.

The at least one vent (3) preferably is in the shape of a wedge with thebroad side at the level of the opening (4) thereof and getting thinneras it penetrates deeper into the vessel, until the two layers meet toform an interface (14) at least at the level of the neck region. Thecontainer may comprise one or several vents evenly distributed aroundthe lip of the bag-in-container's mouth. Several vents are advantageousas they permit the interface of the inner and outer layers (21) and (22)of the bag-in-container (2) to release more evenly upon blowingpressurized gas through said vents. Preferably, the preform comprisestwo vents opening at the vessel's mouth lip at diametrically opposedpositions. More preferably, three, and most preferably, at least fourvents open at regular intervals of the mouth lip.

The wedge shape of the vent is advantageous for the release of theinterface but also for the production of an integral preform. A methodfor producing an integral preform suitable for blow-moulding abag-in-container according to the present invention comprises the stepsof:

-   -   injection moulding the preform's inner layer onto a core;    -   injection moulding the preform's outer layer onto the inner        layer;    -   extracting the thus formed preform from the core,        wherein said core is provided at the base thereof with at least        one pin suitable for forming an interface vent running parallel        to the interface between said first and second layers and        opening to the atmosphere at a location adjacent to and oriented        coaxially with the preform's mouth. The core may comprise a        single pin, but it preferably comprises more than one pin in        order to have several vents opening around the lip of the        container's mouth. The pins preferably have the shape of a wedge        as on the one hand, a wedge shaped vent has the advantages        discussed above and on the other hand, it allows for easier        extraction of the thus produced integral preform from the        mouldcore. The dimensions of the pins depend on the size of the        bag-in-container and, in particular, of the mouth and lip        thereof. For a typical home beverage dispenser of a capacity of        about 56 liters, the pins have a length of about 5 to 75 mm,        preferably 5 to 50 mm, most preferably 10 to 20 mm and their        base, forming the vents openings, preferably are in the shape of        an arc section of length comprised between 3 and 15 mm,        preferably 5 and 10 mm and of width comprised between 0.5 and 5        mm, preferably 0.5 and 2 mm.

The bag-in-container (2) of the present invention can be obtained byproviding a preform as described above; bringing said preform toblow-moulding temperature; fixing the thus heated preform at the levelof the neck region with fixing means in the blow-moulding tool; andblow-moulding the thus heated preform to form a bag-in-container. Theinner and outer layers (21) and (22) of the thus obtainedbag-in-container are connected to one another by an interface (24) oversubstantially the whole of the inner surface of the outer layer. Saidinterface (24) is in fluid communication with the atmosphere through thevents (3), which maintained their original geometry through theblow-moulding process since the neck region of the preform where thevents are located is held firm by the fixing means and is not stretchedsubstantially during blowing.

It is essential that the interface (24) between inner and outer layers(21) and (22) releases upon blowing pressurized gas through the vents inas consistent and reproducible manner. The success of said operationdepends on a number of parameters, in particular, on the interfacialadhesive strength, the number, geometry, and distribution of the vents,and on the pressure of the gas injected. The interfacial strength is ofcourse a key issue and can be modulated by the choice of materials forthe inner and outer layers, and by the process parameters duringblew-moulding. The pressure-time-temperature window used is of course ofprime importance, but it has surprisingly been discovered that excellentresults can be obtained if the blow-moulding process is carried out on apreform as described above, of the type wherein a gap containing airseparates the inner and outer layers over a substantial area of thepreforms body and wherein said gap is in fluid communication with atleast one interface vent and wherein,

-   -   in a first stage, a gas is blown into the space defined by the        inner layer to stretch the preform, whilst the air in the gap        separating the preform inner and outer layers is prevented from        being evacuated by closing said at least one preform interface        vent with a valve located in the fixing means; and    -   in a second stage, when the air pressure building up in said gap        reaches a preset value, the valve opens thus allowing evacuation        of the air enclosed in the gap.        By this method, the inner layer is prevented from entering into        contact with the outer layer by the air cushion enclosed within        the gap separating the two layers when their respective        temperatures are the highest. As stretching proceeds, the gap        becomes thinner and air pressure within the gap increases. When        the pressure reaches a preset value, the valve closing the vent        opening releases, the air is ejected, and the inner layer is        permitted to contact the outer layer and form an interface        therewith at a stage where their respective temperatures have        dropped to a level where adhesion between the layers cannot        build up to any substantial level.

Alternatively or additionally, it is preferred to apply a (mechanical)pressure on the neck region of the inner layer in a direction asindicated by the arrows P in FIG. 1A after or during blow moulding. Ithas surprisingly been found that the application of such pressurefacilitates release of the interface during the blow-moulding operation,hence further release upon blowing pressurized gas through the vents.Indeed, the application of such pressure on the neck portion of theinner layer allows to induce an spacing between the inner and outerlayers at the shoulder portion of the bag-in-container, which spacingfacilitates further delamination of the inner and outer layers uponblowing pressurized gas through the above mentioned vents.

A preform according to the present invention was produced by injecting amelt into a first mould cavity cooled at a temperature of T_mould ° C.,to form the preform's inner layer (11). A melt was injected into asecond mould cavity cooled to form the preforms outer layer (12). Thetwo preform components were assembled to form a preform according to thepresent invention.

The preform produced as explained above was heated in an oven comprisingan array of IRlamps and then fixed into a blow-moulding mould whichwalls were maintained at a desired temperature. Air was blown into thepreform under pressure. The thus produced bag-in-container was theyfilled with a liquid and connected to an appliance for dispensingbeverage comprising a source of compressed air in order to determine thedelamination pressure.

The delamination pressure was determined as follows. The interface ventsof said bag-in-container were connected to the source of compressed air.Air was injected through the vents at a constant pressure, and theinterface between inner and outer layers was observed. The pressure wasincreased stepwise until delamination pressure was reached. Delaminationpressure is defined as the pressure at which the inner bag separatesfrom the outer layer over the whole of their interface and collapses.The surfaces of the thus separated layers were examined for traces ofbonding.

The delamination pressure of the bag-in-container described above was ofabout 0.5±0.1 bar overpressure and showed little trace of cohesivefracture between the inner and outer layers. This example demonstratesthat bag-in-containers of excellent quality can be produced withintegral preforms according to the present invention.

The invention claimed is:
 1. A preform for blow-moulding a bag-in-container, said bag-in-container comprising: an inner layer forming the bag and an outer layer forming the container, and a mouth fluidly connecting the volume defined by the bag to the atmosphere, said container having at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere; and said at least one vent runs parallel to the interface between inner and outer layers and opens to the atmosphere at a location adjacent to, and oriented approximately coaxially with said bag-in-container's mouth; said preform includes the inner layer and the outer layer, and a body, a neck region, and the mouth fluidly connecting the space defined by said inner layer to the atmosphere, wherein said inner and outer layers are connected to one another by an interface at least at the level of the neck region, said preform includes the at least one interface vent running parallel to said interface and opening to the atmosphere at a location adjacent to, and oriented coaxially with said preform's mouth.
 2. The preform according to claim 1, wherein the inner and outer layers consist of different materials.
 3. The preform according to claim 1, wherein the inner and outer layers consist of the same material.
 4. The preform according to claim 1, wherein the inner and outer layers consist of a material selected from PET, PEN, PTT, PA, PP, PE, HDPE, EVOH, PGAc, PLA, and copolymers or blends thereof.
 5. The preform according to claim 1, wherein the at least one vent is in the shape of a wedge with the broad side at the level of the opening thereof and getting thinner as it penetrates deeper into the vessel, until the inner and outer layers meet to form an interface.
 6. The preform according to claim 1, wherein more than one vent is distributed around the lip of the preform's mouth.
 7. The preform according to claim 1, wherein the inner and outer layers of the preform are connected by an interface throughout substantially the whole inner surface of the outer layer.
 8. The preform according to claim 1, wherein the inner and outer layers of the preform are separated over a substantial area of the preform's body by a gap containing air and which is in fluid communication with at least one interface vent.
 9. The preform according to claim 1, having an assembly of two separate inner and outer preforms fitted into one another.
 10. The preform according to claim 1, having an integral preform obtained by injection moulding one layer on top of the other. 